I'm playing Witcher 2 in OSX on my base 27 inch (didn't want to pay £320 more to upgrade to higher version and add on 680 which is what it costs in UK for what will be sparodic gaming) and it plays pretty good. I have it on high settings, but the resolution at 1280 x 720- no problems with it at all. The lack of RAM on the card only makes a difference if you go for native resolution. It looks fine at 1280x720. So anyone worried about gaming on base 27 inch iMac- don't- unless you want the most demanding games on the native resolution. I have Fusion and upgraded the RAM to 24GB- don't think the RAM makes much if any difference to performance of Witcher 2 though.